U.S. patent application number 15/877983 was filed with the patent office on 2018-07-26 for electrode with cellulose acetate separator system.
The applicant listed for this patent is ZAF Energy Systems, Incorporated. Invention is credited to Sean Barrett, Cody R. Carter, William A. Garcia, Adam Weisenstein.
Application Number | 20180212221 15/877983 |
Document ID | / |
Family ID | 62907284 |
Filed Date | 2018-07-26 |
United States Patent
Application |
20180212221 |
Kind Code |
A1 |
Barrett; Sean ; et
al. |
July 26, 2018 |
ELECTRODE WITH CELLULOSE ACETATE SEPARATOR SYSTEM
Abstract
An electrode assembly includes an electrode saturated with
electrolyte, and one or more ionically conductive and
electronically insulating cellulose acetate coatings forming a
continuous and conformal film adhered to and encapsulating the
electrode.
Inventors: |
Barrett; Sean; (Bigfork,
MT) ; Weisenstein; Adam; (Kalispell, MT) ;
Carter; Cody R.; (Kalispell, MT) ; Garcia; William
A.; (Columbia Falls, MT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZAF Energy Systems, Incorporated |
Columbia Falls |
MT |
US |
|
|
Family ID: |
62907284 |
Appl. No.: |
15/877983 |
Filed: |
January 23, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62449281 |
Jan 23, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2/145 20130101;
H01M 2/1606 20130101; H01M 4/244 20130101; H01M 2/1626 20130101;
H01M 10/30 20130101; H01M 2/1673 20130101; H01M 2/1686 20130101;
H01M 2/1653 20130101; H01M 4/26 20130101; H01M 4/42 20130101; Y02E
60/10 20130101 |
International
Class: |
H01M 2/16 20060101
H01M002/16; H01M 10/30 20060101 H01M010/30 |
Claims
1. An electrode assembly comprising: an electrode saturated with
electrolyte; and one or more ionically conductive and
electronically insulating cellulose acetate coatings forming a
continuous and conformal film adhered to and encapsulating the
electrode.
2. The electrode assembly of claim 2, wherein at least some of the
coatings are cellulose diacetate coatings or cellulose triacetate
coatings.
3. The electrode assembly of claim 2, wherein the electrode is a
positive electrode or a negative electrode.
4. The electrode assembly of claim 2, wherein the coatings are
applied via dip coating, screen printing, slurry casting, spin
coating, or spraying.
5. An electrode assembly comprising: an electrode saturated with
electrolyte; and one or more fibrous layers impregnated with
cellulose acetate and encompassing the electrode.
6. The electrode assembly of claim 5, wherein the fibrous layers
form a continuous and conformal layer on the electrode.
7. The electrode assembly of claim 5, wherein the cellulose acetate
is cellulose diacetate or cellulose triacetate.
8. The electrode assembly of claim 5, wherein the electrode is a
positive electrode or a negative electrode.
9. The electrode assembly of claim 5, wherein the fibrous layers
are impregnated by dip coating, screen printing, slurry casting,
spin coating, or spraying.
10. The electrode assembly of claim 5, wherein the fibrous layers
are saturated with the electrolyte.
11. The electrode assembly of claim 5, wherein the fibrous layers
are wrapped around the electrode.
12. The electrode assembly of claim 5, wherein the fibrous layers
are heat sealed to each other.
13. The electrode assembly of claim 5, wherein the fibrous layers
are sealed to each other via an adhesive.
14. An electrode assembly comprising: an electrode saturated with
electrolyte; and one or more ionically conductive and
electronically insulating cellulose acetate sheets encompassing the
electrode.
15. The electrode assembly of claim 14, wherein the cellulose
acetate sheets form a pouch.
16. The electrode assembly of claim 14, wherein at least some of
the cellulose acetate sheets are cellulose diacetate sheets or
cellulose triacetate sheets.
17. The electrode assembly of claim 14, wherein the electrode is a
positive electrode or a negative electrode.
18. The electrode assembly of claim 14, wherein the cellulose
acetate sheets are in contact with the electrode.
19. The electrode assembly of claim 14, wherein the sheets are
wrapped around the electrode.
20. The electrode assembly of claim 14, wherein the sheets are heat
sealed to each other.
21. The electrode assembly of claim 14, wherein the sheets are
sealed to each other via an adhesive.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/449281, filed Jan. 23, 2017, the disclosure of
which is hereby incorporated in its entirety by reference
herein.
TECHNICAL FIELD
[0002] This disclosure relates to batteries and electrodes
therefor.
BACKGROUND
[0003] Primary cells are designed to be used once and discarded.
Generally speaking, the electrochemical reactions occurring in the
cells are not reversible: As a primary cell is used, the reactions
therein use up the chemicals that generate power and irreversible
reaction products.
[0004] Secondary cells facilitate reversible cell reactions that
allow them to recharge, or regain their cell potential, through the
work done by passing currents and converting the products back to
reactant status. As opposed to primary cells that experience
irreversible electrochemical reactions such as gassing, secondary
cell reactions can be reversed allowing for numerous charges and
discharges.
SUMMARY
[0005] An electrode assembly includes an electrode saturated with
electrolyte, and one or more ionically conductive and
electronically insulating cellulose acetate coatings forming a
continuous and conformal film adhered to and encapsulating the
electrode. At least some of the coatings may be cellulose diacetate
coatings or cellulose triacetate coatings. The electrode may be a
positive electrode or a negative electrode. The coatings may be
applied via dip coating, screen printing, slurry casting, spin
coating, or spraying.
[0006] An electrode assembly includes an electrode saturated with
electrolyte, and one or more fibrous layers impregnated with
cellulose acetate and encompassing the electrode. The fibrous
layers may form a continuous and conformal layer on the electrode.
The cellulose acetate may be cellulose diacetate or cellulose
triacetate. The electrode may be a positive electrode or a negative
electrode. The fibrous layers may be impregnated by dip coating,
screen printing, slurry casting, spin coating, or spraying. The
fibrous layers may be saturated with the electrolyte. The fibrous
layers may be wrapped around the electrode. The fibrous layers may
be heat sealed to each other. The fibrous layers may be sealed to
each other via an adhesive.
[0007] An electrode assembly includes an electrode saturated with
electrolyte, and one or more ionically conductive and
electronically insulating cellulose acetate sheets encompassing the
electrode. The cellulose acetate sheets may form a pouch. At least
some of the cellulose acetate sheets may be cellulose diacetate
sheets or cellulose triacetate sheets. The electrode may be a
positive electrode or a negative electrode. The cellulose acetate
sheets may be in contact with the electrode. The sheets may be
wrapped around the electrode. The sheets may be heat sealed to each
other. The sheets may be sealed to each other via an adhesive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic diagram of a battery.
[0009] FIGS. 2, 3, 5, and 6 are side views, in cross-section, of
portions of other batteries.
[0010] FIG. 4 is a side view, in cross-section, of the portion of
the battery of FIG. 3 in stacked configuration.
[0011] FIG. 7 is a plot of cycle life testing for nickel-zinc pouch
cells.
DETAILED DESCRIPTION
[0012] Various embodiments of the present disclosure are described
herein. However, the disclosed embodiments are merely exemplary and
other embodiments may take various and alternative forms that are
not explicitly illustrated or described. The figures are not
necessarily to scale; some features may be exaggerated or minimized
to show details of particular components. Therefore, specific
structural and functional details disclosed herein are not to be
interpreted as limiting, but merely as a representative basis for
teaching one of ordinary skill in the art to variously employ the
present invention. As those of ordinary skill in the art will
understand, various features illustrated and described with
reference to any one of the figures may be combined with features
illustrated in one or more other figures to produce embodiments
that are not explicitly illustrated or described. The combinations
of features illustrated provide representative embodiments for
typical applications. However, various combinations and
modifications of the features consistent with the teachings of this
disclosure may be desired for particular applications or
implementations.
[0013] Referring to FIG. 1, a battery 10 in concept includes an
anode 12, cathode 14, and separator 16 disposed therebetween. These
components may be separately or collectively bathed in electrolyte
18, and contained by housing 19. The anode 12, cathode 14, and
separator 16 may be referred to as an electrode assembly 20, and be
electrically connected via circuitry 22. The separator 16
physically separates the anode 12 and cathode 14. Ions, however,
travel thereacross. During discharge, ions may travel from the
cathode 14, through the separator 16, and to the anode 12. During
charge, the ions may travel from the anode 12, through the
separator 16, and to the cathode 14. The flow of current through
the circuitry 22 accompanies this process.
[0014] Typical separators for zinc chemistry batteries include
combinations of microporous polymer layers, which help to stop zinc
dendrites from reaching the positive electrode and thus shorting
the battery. These layers are robust and create long tortuous paths
for zinc dendrites to have to penetrate though. Here, however,
cellulose acetate as a stand-alone separator has been found to
yield superior results in preventing shorting as compared to
typical microporous separators, and to contribute to substantial
increases in capacity retention during cycling. This was previously
not thought possible due to the low strength nature and low
porosity of cellulose acetate. In spite of sub-prime mechanical
properties, this material is unexpectedly able to discourage
dendritic shorting. Cellulose acetate has small pores, which are
smaller than typical separators (e.g., 50 nm or smaller pores.)
These pores are even smaller than the soluble zincate ions formed
during both charge and discharge of the zinc electrode. Hence it
can block the zincate ions from moving from the negative to the
positive electrode. Additionally, cellulose acetate is ionically
conductive, electronically insulating, and stable in an alkaline
environment. Moreover, cellulose acetate has been found to be heat
sealable and amenable to creating, for example, a sealed separator
envelope around negative electrodes.
[0015] In certain embodiments, a cellulose triacetate layer (or
layers) may be used as a separator (e.g., a coating or layer
separating the anode and cathode, a sealed (adhesive or heat) pouch
to contain the anode, a wrapping around the anode, etc.). In other
embodiments, a cellulose acetate or cellulose diacetate layer (or
layers), or combinations of cellulose acetate, cellulose diacetate,
and cellulose triacetate layers may be similarly used. Cellulose
triacetate, in certain environments, may be preferred to cellulose
diacetate as it is mechanically stronger and more stable at
elevated temperatures. Such separators may, of course, be
synthesized with a chemically compatible binder/plasticizer, such
as carboxymethyl cellulose, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, etc.
[0016] Referring to FIG. 2, a battery 110 includes an anode
(negative electrode) structure 112 and a cathode (positive
electrode) structure 114. In this example, the anode structure 112
includes active material particles 124 (e.g., aluminum, iron, zinc,
etc.) held together via a binder or plasticizer 126 (e.g., acrylic
binders, aromatic binders, carboxymethyl cellulose,
perfluoropolyether, polyethylene glycol, polytetrafluoroethylene,
polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride,
urethanes, various ionomers, etc.) to form a porous structure
defining void spaces occupied by electrolyte 118 (e.g., alkaline).
This structure and the electrolyte 118 are contained by a cellulose
acetate pouch 116, which acts as a separator from the cathode
structure 114. The pouch 116, in this example, comprises two sheets
of a single monolayer of cellulose triacetate encapsulating the
porous structure and electrolyte 118, and sealed (e.g., heat
sealed) around a perimeter 130 thereof. In other examples, a single
sheet (having a single layer or multiple layers) may be wrapped or
adhesively sealed around the porous structure and electrolyte 118.
In other examples, the pouch 116 may be comprised of cellulose
acetate sheet(s) containing a fibrous substrate which can add
structural integrity and/or improve wicking of the electrolyte 118.
Other arrangements are also possible.
[0017] The cathode structure 114 includes a scaffold 132 (e.g.,
carbon fiber, carbon foam, conductive ceramics, conductive
plastics, copper or nickel fiber, copper or nickel foam, copper or
nickel mesh, copper or nickel punched metal, expanded metal, gold
plated structures, platinum plated steel (or other metal), sintered
nickel powder, titanium fibers, etc.), catalyst particles 134
(e.g., activated carbons, carbon blacks, graphites, hard carbons,
hydroxides, metal oxides, perovskites, spinels, etc.) in contact
with the scaffold 132, and a binder or plasticizer 136 (e.g.,
acrylic binders, aromatic binders, carboxymethyl cellulose,
perfluoropolyether, polyethylene glycol, polytetrafluoroethylene,
polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride,
urethanes, various ionomers, etc.) connecting the particles 134 to
the scaffold 132. (Other cathode structures are of course
contemplated.) A porosity of the scaffold 132 is such that void
spaces (fluid passageways) facilitate flow therethrough.
[0018] The battery 110 further includes anode and cathode current
collector tabs 138, 140 extending respectively away from the anode
and cathode structures 112, 114, and circuitry 122 to facilitate
the flow of current during operation. The pouch 116 is sealed to
itself and around the anode current collector tab 138.
[0019] Referring to FIG. 3, a battery 210 includes an anode
structure 212 and a cathode structure 214. In this example, the
anode structure 212 includes active material particles 224 (e.g.,
aluminum, iron, zinc, etc.) held together via a binder or
plasticizer 226 (e.g. acrylic binders, aromatic binders,
carboxymethyl cellulose, perfluoropolyether, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, polyvinyl chloride,
polyvinylidene fluoride, various ionomers, urethanes, etc.) to form
a porous structure defining void spaces occupied by electrolyte 218
(e.g., alkaline). This structure and the electrolyte 218 are
contained by a cellulose acetate pouch 216, which acts as a
separator from the cathode structure 214. The pouch 216, in this
example, comprises two sheets of a single monolayer of cellulose
triacetate sandwiching the porous structure and electrolyte 218,
and sealed (e.g., heat sealed) around a perimeter 230 thereof. In
other examples, a single sheet (having a single layer or multiple
layers) may be wrapped or adhesively sealed around the porous
structure and electrolyte 218. In some examples, the pouch 216 may
be comprised of cellulose acetate sheet(s) containing a fibrous
substrate which can add structural integrity and/or improve wicking
of the electrolyte 218. The cathode structure 214 includes active
material particles 242 (e.g., hydroxides (e.g., M(OH).sub.2, where
M=Al, Co, Fe, Mn, Ni, etc.)) held together via a binder or
plasticizer 244 (e.g., acrylic binders, aromatic binders,
carboxymethyl cellulose, perfluoropolyether, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, polyvinyl chloride,
polyvinylidene fluoride, urethanes, various ionomers, etc.) to form
a porous structure defining void spaces occupied by electrolyte 246
(e.g. alkaline).
[0020] The battery 210 further includes anode and cathode current
collector tabs 238, 240 extending respectively away from the anode
and cathode structures 212, 214, and circuitry 222 to facilitate
the flow of current during operation. The pouch 216 is sealed to
itself and around the anode current collector tab 238.
[0021] Referring to FIG. 4, the anode and cathode structures 212,
214 may be stacked in an alternating fashion to increase battery
capacity. Here again, the pouches 216 act as a separator between
the anode and cathode structures 212, 214.
[0022] Referring to FIG. 5, a battery 310 includes an anode
structure 312 and a cathode structure 314. In this example, the
anode structure 312 includes active material particles 324 (e.g.,
aluminum, iron, zinc, etc.) held together via a binder or
plasticizer 326 (e.g., acrylic binders, aromatic binders,
carboxymethyl cellulose, perfluoropolyether, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, polyvinyl chloride,
polyvinylidene fluoride, urethanes, various ionomers, etc.) to form
a porous structure defining void spaces occupied by electrolyte 318
(e.g., alkaline). The cathode structure 314 includes active
material particles 342 (e.g., hydroxides (e.g., M(OH).sub.2, where
M=Al, Co, Fe, Mn, Ni, etc.)) held together via a binder or
plasticizer 344 (e.g., acrylic binders, aromatic binders,
carboxymethyl cellulose, perfluoropolyether, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, polyvinyl chloride,
polyvinylidene fluoride, urethanes, various ionomers, etc.) to form
a porous structure defining void spaces occupied by electrolyte 346
(e.g., alkaline). This structure and the electrolyte 346 are
contained by a cellulose acetate wrapping 316, which acts as a
separator from the anode structure 312. In some examples, the
wrapping 316 includes one or more layers of cellulose acetate wound
as one may wind a package with shrink wrap for safe shipping, etc.
In some examples, the wrapping 316 may be comprised of cellulose
acetate sheet(s) containing a fibrous substrate which can add
structural integrity and/or improve wicking of the electrolyte 346.
The battery 310 further includes anode and cathode current
collector tabs 338, 340 extending respectively away from the anode
and cathode structures 312, 314, and circuitry 322 to facilitate
the flow of current during operation. In circumstances in which the
current collector tab 340 pierces the wrapping 316, a sealant may
be applied therearound to maintain the integrity of the effective
container formed by the wrapping 316.
[0023] Referring to FIG. 6, a battery 410 includes an anode
structure 412 and a cathode structure 414. In this example, the
anode structure 412 includes active material particles 424 (e.g.,
aluminum, zinc, and iron, etc.) held together via a binder or
plasticizer 426 (e.g., acrylic binders, aromatic binders,
carboxymethyl cellulose, perfluoropolyether, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, polyvinyl chloride,
polyvinylidene fluoride, various ionomers, urethanes, etc.) to form
a porous structure defining void spaces occupied by electrolyte 418
(e.g., alkaline). The cathode structure 414 includes active
material particles 442 (e.g., hydroxides (e.g., M(OH).sub.2, where
M=Al, Co, Fe, Mn, Ni, etc.)) held together via a binder or
plasticizer 444 (e.g., acrylic binders, aromatic binders,
carboxymethyl cellulose, perfluoropolyether, polyethylene glycol,
polytetrafluoroethylene, polyvinyl alcohol, polyvinyl chloride,
polyvinylidene fluoride, urethanes, various ionomers, etc.) to form
a porous structure defining void spaces occupied the electrolyte
418. Each of the structures 412, 414 and the electrolyte 418
therein are contained by respective cellulose acetate coatings 416
that form respective continuous and conformal films adhered to and
encapsulating the respective structures 412, 414. In some examples,
the structures 412, 414 and electrolyte 418 therein may be
contained in a cellulose acetate coating 416 through a fibrous
layer which can act as a wicking agent for the electrolyte 418
and/or give structural integrity to the coating, while maintaining
a continuous and conformal film adhered to and in contact with the
respective structures 412, 414. The battery 410 further includes a
separator system of microporous sheets 448 around the cellulose
acetate coatings 416. And, anode and cathode current collector tabs
438, 440 extending respectively away from the anode and cathode
structures 412, 414, and circuitry 422 to facilitate the flow of
current during operation. In circumstances in which the current
collector tabs 438, 440 pierce the cellulose acetate coatings 416,
a sealant may be applied therearound to maintain the integrity of
the effective container formed by the cellulose acetate coatings
416.
[0024] Tests with nickel-zinc pouch cells were conducted with
standard separator systems and modified separator systems utilizing
cellulose acetate coatings on the electrodes. Both separator
systems included two layers of microporous separators and two
electrolyte reservoir layers. The modified separator system also
included cellulose acetate dip coated electrodes, which formed a
film adhered to and encapsulating the electrodes. These cells were
cycled at a C/3 rate for both charge and discharge to 100% depth of
discharge, based on a name plate rated capacity. The testing of
cells containing the modified separator system resulted in a gain,
over the standard separator system, of 9.3% in cycle life to 80%
utilization and 10.8% gain in overall energy during those cycles as
shown in FIG. 7.
[0025] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms
encompassed by the claims. The words used in the specification are
words of description rather than limitation, and it is understood
that various changes may be made without departing from the spirit
and scope of the disclosure and claims. As previously described,
the features of various embodiments may be combined to form further
embodiments that may not be explicitly described or illustrated.
While various embodiments may have been described as providing
advantages or being preferred over other embodiments or prior art
implementations with respect to one or more desired
characteristics, those of ordinary skill in the art recognize that
one or more features or characteristics may be compromised to
achieve desired overall system attributes, which depend on the
specific application and implementation. These attributes include,
but are not limited to appearance, cost, durability, ease of
assembly, life cycle cost, manufacturability, marketability,
packaging, serviceability, size, strength, weight, etc. As such,
embodiments described as less desirable than other embodiments or
prior art implementations with respect to one or more
characteristics are not outside the scope of the disclosure and may
be desirable for particular applications.
* * * * *